The present invention relates to flexible duct in the form of convolutely-wound or helical formed bodies, and in particular, to an improved apparatus and method for making flexible, wire-reinforced duct of the type used in air-conditioning and/or heating applications, agriculture irrigation, and miscellaneous industrial or like applications wherein the duct is surrounded with insulation blanket or layer, such as fiberglas, or the like, which may be covered with an outer protective vapor barrier, such as vinyl sheathing or the like.
Heretofore, flexible hose has been formed from tape which is reinforced with wire along one edge. In such case, the wire-reinforced tape is fed between the nip of a series of rollers, looped back so the end of the tape is re-fed through the rollers to overlap the edge of the tape entering the machine so as to provide a helical form continuous hose. For example, see U.S. Pat. No. 2,674,296. In other methods, the tape is manufactured along both of its edges with wire in the same manner one edge of the tape is reinforced, as in U.S. Pat. No. 2,674,296. The tape is then formed into a helix with its edges overlapping and the two reinforcing wires interlocked to form a joint. For example, see U.S. Pat. No. 3,191,631. Heretofore, such prior apparatus and methods have been unsatisfactory in providing a light-weight, high strength flexible wire-reinforced duct which can be quickly and efficiently produced by high volume production, as will hereinafter be more fully discussed.